fixed!
Note: Make sure you install mkisofs before doing the export, or it will fail at the end.
Exported the RHEL 5 i386 server channel to DVD ISOs. It made two ISOs, one full, and one partial. I then burned the full ISO to a DVD, and confirmed that it could be mounted and the data could be read. No errors. Moving to Verified.
5.1.1 Satellite is now GA, bugs Closed for Current Release.